The Anxiety and Depression Association of America states that major depressive disorder is the leading cause of disability in the US. Now, new research has revealed that it is the second leading cause of disability worldwide. This is according to a study published in the journal PLOS Medicine.

Researchers from the US, Canada and Australia, led by Alize Ferrari of the University of Queensland and the Queensland Center for Mental Health Research, conducted a study that they say reports the most recent and comprehensive estimates on how much death and disability worldwide is a result of depression.

To reach their findings, the research team analyzed information from all published research that studied major depressive disorder and dysthymia – a milder but chronic form of depression.

The researchers added together the “years lived with a disability” (YLDs) and the “years of life lost because of disease-specific premature death” (YLLs) from the studies. This gave them an estimated measure of disease burden, known as “disability-adjusted life years” (DALYs).

Some countries, particularly those that were low-income, presented few published studies to work from, the researchers note. Therefore, the team replaced actual numbers with estimates in order to work out YLDs and DALYs.

They then compared the burden of diseases and injuries worldwide and ranked them in order of their cause.

Depressive disorders are ‘global health priority’

The researchers found that major depressive disorder was the second leading cause of disability worldwide, or YLDs, and the 11th leading cause of global burden, or DALYs, in 2010.

Furthermore, the findings revealed that when adding the DALYs as a result of major depressive disorder to two other conditions – suicide and ischemic heart disease – major depressive disorder ranked as the eighth leading cause of global burden.

When looking at rankings among all causes of disability between different countries and regions, they varied significantly. The rates of disability were highest in Afghanistan and lowest in Japan, while depression as a cause of disability ranked first in Central America and Central and Southeast Asia.

Additionally, disability as a result of depression was found to mainly affect people in their working years, and women were more affected than men.

“Our findings not only highlight the fact that depressive disorders are a global health priority but also that it is important to understand variations in burden by disorder, country, region, age, sex and year when setting global health objectives,” the researchers say.

“Furthermore,” the team adds, “estimating the burden attributable to major depressive disorder as a risk factor for other health outcomes allows for a more accurate estimate of burden and reinforces the importance of implementing cost effectiveness interventions to reduce its ubiquitous burden.”

The researchers conclude that further improvements to the way the global burden of disease is measured, as well as access to more data detailing the effects of health and disease conditions within populations, will “enhance the precision” of burden estimates and create a better understanding surrounding the global burden of depressive disorders.